improve calculation

src/Ema.php

@@ -18,24 +18,15 @@ public function calculate(array $values, int $period = 9) : float
 		}
 
 		$mult = 2 / ($period + 1);
-		$prev_close = [];
-		$prev_ema = false;
+		$ema = 0;
 		foreach ($values as $value) {
 			if ( !is_numeric($value)) {
 				throw new \Exception('[' . __METHOD__ . '] invalid value: '. $value);
 			}
 
-			if (count($prev_close) < $period) {
-				$prev_close[] = $value;
-				if (count($prev_close) === $period) {
-					$prev_ema = array_sum($prev_close) / $period;
-				}
-				continue;
-			}
-
-			$prev_ema = ($value - $prev_ema) * $mult + $prev_ema;
+			$ema = ($value - $ema) * $mult + $ema;
 		}
 
-		return $prev_ema;
+		return $ema;
 	}
 }

tests/TestEma.php

@@ -6,20 +6,7 @@
 
 final class EmaTest extends TestCase
 {
-	public function testCalculateEmaWithEmptyPreviousValues(): void
-	{
-		$val = require(__DIR__ . '/values.php');
-		$values = [];
-		foreach ($val as $v) {
-			$values[] = $v[2];
-		}
-		$values = array_slice($values, -9);
-
-		$ema = new Ema();
-		$this->assertSame(9147.33, round($ema->calculate($values), 2));
-	}
-
-	public function testCalculateEmaWithMorePreviousValues(): void
+	public function testCalculateWithMorePreviousValues(): void
 	{
 		$val = require(__DIR__ . '/values.php');
 		$values = [];
@@ -31,15 +18,15 @@ public function testCalculateEmaWithMorePreviousValues(): void
 		$this->assertSame(9101.36, round($ema->calculate($values), 2));
 	}
 
-	public function testCalculateEmaWithEmptyArray(): void
+	public function testCalculateWithEmptyArray(): void
 	{
 		$this->expectException(Exception::class);
 
 		$ema = new Ema();
 		$ema->calculate([]);
 	}
 
-	public function testCalculateEmaWithInvalidArray(): void
+	public function testCalculateWithInvalidArray(): void
 	{
 		$values = [
 			9148.27,